Inlet guide vane retention feature

ABSTRACT

A variable vane assembly includes a vane having a trunnion. The trunnion includes a partial flange. A shroud supporting the trunnion in a recess has a forward axial half and an aft axial half. The recess includes a retainer portion which receives the partial flange. An engine and a vane are also described.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application No. 61/765,744, filed Feb. 17, 2013.

BACKGROUND OF THE INVENTION

This application relates to a retention feature for an inlet guide vane.

Gas turbine engines are known and typically include a fan delivering air into a compressor section where the air is compressed and passed into a combustor section. The air is mixed with fuel and ignited and products of this combustion pass downstream over turbine rotors, driving the turbine rotors to rotate.

The turbine rotors, in turn, drive the fan and compressor section. Historically, a turbine rotor drove a low pressure compressor and a fan at a single speed. More recently, a gear reduction has been placed between the turbine driving the fan and this allows the fan to rotate at slower speeds.

Rotating the fan at slower speeds has allowed the diameter of the fan to increase. It is known for the fan to deliver air into a bypass duct, where it becomes propulsion for an associated aircraft and into a core flow to the compressor. The fans which are provided with a gear reduction may have relatively high bypass ratios, or the volume of the air delivered into the bypass duct compared to the volume of air delivered into the compressor.

As the volume of air delivered into the compressor becomes a smaller percentage, it becomes more important to utilize the core air efficiently. The compressor and turbine sections are provided with a plurality of rotating blades and vanes spaced between the rows of the blades. The vanes serve to direct and control the flow of air between stages or rows of the blades.

One type of vane is a variable vane. In a variable vane, a vane pivots relative to a radial axis taken from a central axis of the engine. An actuator rotates a first side of the vane to pivot and a second opposed side of the vane is supported for rotation in a shroud. Typically, the actuator is at a radially outer location.

In the event of a variable inlet vane failure, the first rotated and second supported sides of the vane may become disconnected from one another. The second supported side of the vane may become liberated from the shroud and may be ingested by the rotating fan or other downstream rotating engine components.

Due to limited space available on the shroud and the angle of vane with respect to the engine axis, it is difficult to incorporate retention features in the shroud to prevent the second supported side of the vane from detaching from the shroud.

SUMMARY OF THE INVENTION

In a featured embodiment, a variable vane assembly includes a vane having a trunnion. The trunnion includes a partial flange. A shroud has a forward axial half and an aft axial half, and supports the trunnion in a recess. The recess includes a retainer portion receiving the partial flange.

In another embodiment according to the previous embodiment, the variable vane assembly additionally includes a second trunnion, and an actuator connected to the second trunnion for causing the vane to pivot to change an angle of incidence.

In another embodiment according to any of the previous embodiments, the second trunnion is an outer trunnion.

In another embodiment according to any of the previous embodiments, the aft axial half includes the retainer portion.

In another embodiment according to any of the previous embodiments, the retainer portion is a recess extending from a central bore for a first limited circumferential extent of the central bore.

In another embodiment according to any of the previous embodiments, the partial flange extends from the trunnion for a second limited circumferential extent, where the second limited circumferential extent of the partial flange is less than the first limited circumferential extent of the retainer portion.

In another embodiment according to any of the previous embodiments, the trunnion can pivot relative to a central axis of the central bore when the partial flange is received in the retainer portion.

In another embodiment according to any of the previous embodiments, the retainer portion is defined by a bottom wall and a ledge.

In another embodiment according to any of the previous embodiments, the variable vane assembly is for use in a compressor section.

In another embodiment according to any of the previous embodiments, the variable vane assembly further includes a means to limit rotation of the vane about a central axis of the trunnion.

In another embodiment according to any of the previous embodiments, the partial flange has a substantially curvic profile in the plane perpendicular to a central axis of the trunnion.

In another embodiment according to any of the previous embodiments, the partial flange has a substantially faceted profile in the plane perpendicular to a central axis of the trunnion.

In another featured embodiment, a gas turbine engine includes a compressor section and a variable vane assembly in the compressor section. The variable vane assembly includes a plurality of vanes having an inner trunnion and an outer trunnion. The inner trunnion includes a partial flange extending from the inner trunnion for a first limited circumferential extent. An actuator is connected to the outer trunnion for causing the vane to pivot to change an angle of incidence. A shroud has a forward axial half and an aft axial half, and supports the inner trunnion in recesses. The recesses include a retainer portion in the aft axial half receiving the partial flange. The retainer portion is a recess defined by a bottom wall and a ledge. The retainer portion extends from a central bore for a second limited circumferential extent greater than the first circumferential extent of the partial flange. The inner trunnion can pivot relative to a central axis of the central bore when the partial flange is received in the retainer portion.

In another embodiment according to any of the previous embodiments the gas turbine engine further includes a means to limit rotation of the vane about the central axis.

In another embodiment according to any of the previous embodiments, the variable vane assembly is rotatable to first and second positions, wherein said first and second positions correspond to first and second ends of said second limited circumferential extent, respectively.

In another embodiment according to any of the previous embodiments, the partial flange has a substantially curvic profile in the plane perpendicular to the central axis.

In another embodiment according to any of the previous embodiments, the partial flange has a substantially faceted profile in the plane perpendicular to the central axis.

In another featured embodiment, a variable vane includes a vane having an airfoil, the vane having a first end and a second end, a first trunnion attached to the first end of the vane, adapted to accept a force from an actuator to cause a rotational moment to be applied to said vane about a central axis, and a second trunnion attached to the second end of the vane, comprising a first portion that is substantially cylindrical, and a partial flange extending from the first portion of the second trunnion for a limited circumferential extent relative to the central axis.

In another embodiment according to any of the previous embodiments, the partial flange has a substantially curvic profile in the plane perpendicular to the central axis.

In another embodiment according to any of the previous embodiments, the partial flange has a substantially faceted profile in the plane perpendicular to the central axis.

The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation of the invention will become more apparent in light of the following description and the accompanying drawings. It should be understood, however, that the following description and drawings are intended to be exemplary in nature and non-limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings that accompany the detailed description can be briefly described as follows:

FIG. 1 schematically shows a gas turbine engine.

FIG. 2 schematically shows a variable vane assembly.

FIG. 3 a schematically shows a detail view of the variable vane assembly of FIG. 3.

FIG. 3 b schematically shows an alternate detail view of the variable vane assembly of FIG. 2.

FIG. 3 c schematically shows an alternative partial flange.

FIG. 4 schematically shows a shroud for receiving the variable vane assembly of FIG. 2.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a gas turbine engine 20. The gas turbine engine 20 is disclosed herein as a two-spool turbofan that generally incorporates a fan section 22, a compressor section 24, a combustor section 26 and a turbine section 28. Alternative engines might include an augmentor section (not shown) among other systems or features. The fan section 22 drives air along a bypass flow path B in a bypass duct defined within a nacelle 15, while the compressor section 24 drives air along a core flow path C for compression and communication into the combustor section 26 then expansion through the turbine section 28. Although depicted as a turbofan gas turbine engine in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of turbine engines including three-spool architectures.

The engine 20 generally includes a low speed spool 30 and a high speed spool 32 mounted for rotation about an engine central longitudinal axis A relative to an engine static structure 36 via several bearing systems 38. It should be understood that various bearing systems 38 at various locations may alternatively or additionally be provided.

The low speed spool 30 generally includes an inner shaft 40 that interconnects a fan 42, a low pressure compressor 44 and a low pressure turbine 46. The inner shaft 40 is connected to the fan 42 through a geared architecture 48 to drive the fan 42 at a lower speed than the low speed spool 30. The high speed spool 32 includes an outer shaft 50 that interconnects a high pressure compressor 52 and high pressure turbine 54. A combustor 56 is arranged between the high pressure compressor 52 and the high pressure turbine 54. A mid-turbine frame 57 of the engine static structure 36 is arranged generally between the high pressure turbine 54 and the low pressure turbine 46. The mid-turbine frame 57 further supports bearing systems 38 in the turbine section 28. The inner shaft 40 and the outer shaft 50 are concentric and rotate via bearing systems 38 about the engine central longitudinal axis A which is collinear with their longitudinal axes.

The core airflow is compressed by the low pressure compressor 44 then the high pressure compressor 52, mixed and burned with fuel in the combustor 56, then expanded over the high pressure turbine 54 and low pressure turbine 46. The mid-turbine frame 57 includes airfoils 59 which are in the core airflow path. The turbines 46, 54 rotationally drive the respective low speed spool 30 and high speed spool 32 in response to the expansion.

The engine 20 in one example is a high-bypass geared aircraft engine. In a further example, the engine 20 bypass ratio is greater than about six (6), with an example embodiment being greater than ten (10), the geared architecture 48 is an epicyclic gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about 2.3 and the low pressure turbine 46 has a pressure ratio that is greater than about 5. In one disclosed embodiment, the engine 20 bypass ratio is greater than about ten (10:1), the fan diameter is significantly larger than that of the low pressure compressor 44, and the low pressure turbine 46 has a pressure ratio that is greater than about 5:1. Low pressure turbine 46 pressure ratio is pressure measured prior to inlet of low pressure turbine 46 as related to the pressure at the outlet of the low pressure turbine 46 prior to an exhaust nozzle. The geared architecture 48 may be an epicycle gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about 2.5:1. It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present invention is applicable to other gas turbine engines including direct drive turbofans.

A significant amount of thrust is provided by the bypass flow B due to the high bypass ratio. The fan section 22 of the engine 20 is designed for a particular flight condition—typically cruise at about 0.8 Mach and about 35,000 feet. The flight condition of 0.8 Mach and 35,000 ft, with the engine at its best fuel consumption—also known as “bucket cruise Thrust Specific Fuel Consumption (‘TSFC’)”—is the industry standard parameter of 1 bm of fuel being burned divided by 1 bf of thrust the engine produces at that minimum point. “Low fan pressure ratio” is the pressure ratio across the fan blade alone, without a Fan Exit Guide Vane (“FEGV”) system. The low fan pressure ratio as disclosed herein according to one non-limiting embodiment is less than about 1.45. “Low corrected fan tip speed” is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(Tram ° R)/(518.7° R)]^(0.5). The “Low corrected fan tip speed” as disclosed herein according to one non-limiting embodiment is less than about 1150 ft/second.

FIG. 2 shows a portion of the compressor 24 of FIG. 1. It should be understood that variable vane structures utilized in turbine sections may also benefit from the teachings of this application. As shown, the compressor section may include static vanes 111 and includes rotor blades 112. A variable vane 99 is positioned upstream of the blade 112 and serves to direct the air flow at the blade 112, such that the air flow is directed as would be desired. During different flow operational conditions, it is desirable to change the angle of incident of an airfoil 201 of the vane 99 to achieve differing flow characteristics. The airfoil 201 is that portion of the vane 99 that may be aerodynamically shaped and is, when installed within the engine 20, exposed to the air flow within a gas path. The vane 99 in one aspect is adapted to pivot about a radial axis of the engine 20, originating from the center line of the engine A. In one embodiment, the outer end of the vane 99 has an upper trunnion 97. The upper trunnion 97 is mechanically coupled to an adjustment structure 96. The adjustment structure 96 applies a force to the vane 99 to urge the vane 99 to pivot or resist pivoting of the vane 99 induced by aerodynamic forces generated by the airfoil 201. In one example, the adjustment structure 96 applies a rotational moment to the vane 99.

An inner end of the vane 99 has an inner trunnion 110 received within a shroud 102. In the event of a failure of the vane 99, an outer end may become detached from an inner end. As used herein the relative term ‘outer’ is relatively further away from the center line A (FIG. 1) of the engine 20 as compared to the complementary relative term ‘inner’ with respect to the same feature.

Shroud 102 is axially divided into two halves 104 and 106. Axial half 104 is a forward half of the shroud, while axial half 106 is an aft half of the shroud.

As is shown in FIGS. 3 a and 3 b, in one example, recesses 108 are found in the forward and aft axial halves 104, 106 to support the lower trunnion 110 on the inner end of the vane 99. Inner trunnion 110 may have a reduced diameter at a first portion 113 radially inward from airfoil 201 of the vane 99 that allows inner trunnion 110 to rest on supports 114. A second portion 116 may have a reduced diameter from the first portion 113. In one example, the first and second portions 113 and 116 may be substantially cylindrical.

In one example, inner trunnion 110 may include a partial flange 118. Referring to FIG. 3 b, the partial flange 118 may extend for a limited circumferential distance of a radially innermost end of the inner trunnion 110. The partial flange 118 extends radially outward from the inner trunnion 110 relative to a central axis X for a limited circumferential extent defined between edges 126. The partial flange 118 may be received by a retainer recess or portion 120 in the aft axial half 106 to retain the inner end of the vane 99 in the shroud 102. Of course, the retainer portion 120 may be on the forward axial half 104. Also, it may be that the adjustment structure 96 is connected to the inner trunnion 110 and the shroud 102 supports the outer trunnion 97. Recess 108 may include a central bore defined by a bottom wall 122 and a ledge 124. Retainer portion 120 extends from the central bore for a limited circumferential distance relative to the central axis X. That is, retainer portion 120 extends radially outward from the central bore for a limited circumferential extent defined between edges 128. The partial flange 118 is received between the bottom 122 of the central bore and the ledge 124 and is thus retained or mechanically captured within the retainer portion 120.

In the examples shown in FIGS. 3 b and 4, the retainer portion 120 and the partial flange 118 have generally curved shapes. However, in other examples, the retainer portion 120 and the partial flange 118 may have another shape including shapes such as generally faceted, curvic, rectilinear and combinations thereof. A faceted partial flange 600 is illustrated in FIG. 3 c.

As is shown in FIG. 3 b, the retainer portion 120 extends for a greater circumferential extent than the partial flange 118, allowing the inner trunnion 110 to rotate about the central axis X when the partial flange 118 is retained in the retainer portion 120. Said another way, the circumferential extent of the partial flange 118 as defined between edges 126 is less than the circumferential extent of the retainer portion 120 as defined between edges 128 relative to the central axis X to allow the vane 99 to be driven to rotate by the adjustment structure 96.

As is shown in FIG. 4, plural recesses 108 including retainer portions 120 are circumferentially spaced around the circumference of the shroud 102.

This feature thus retains an inner end of the vane 99.

In the event of a fracture that mechanically breaks the vane 99, thus separating the outer portion of the vane from the inner portion of the vane 99, the remnants of the inner portion of the vane 99 are retained by the retainer portion 120, without adding substantial weight to the shroud 102 or the vane 99.

Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention. 

1. A variable vane assembly comprising: a vane having a trunnion, wherein the trunnion includes a partial flange; and a shroud comprising a forward axial half and an aft axial half, and supporting said trunnion in a recess, wherein said recess includes a retainer portion receiving said partial flange.
 2. The variable vane assembly as set forth in claim 1, additionally including a second trunnion, and an actuator connected to said second trunnion for causing said vane to pivot to change an angle of incidence.
 3. The variable vane assembly as set forth in claim 2, wherein said second trunnion is an outer trunnion.
 4. The variable vane assembly as set forth in claim 1, wherein said aft axial half includes said retainer portion.
 5. The variable vane assembly as set forth in claim 1, wherein said retainer portion is a recess extending from a central bore for a first limited circumferential extent of said central bore.
 6. The variable vane assembly as set forth in claim 5, wherein said partial flange extends from said trunnion for a second limited circumferential extent, wherein the second limited circumferential extent of said partial flange is less than the first limited circumferential extent of said retainer portion.
 7. The variable vane assembly as set forth in claim 6, wherein said trunnion can pivot relative to a central axis of said central bore when said partial flange is received in said retainer portion.
 8. The variable vane assembly as set forth in claim 6, wherein said retainer portion is defined by a bottom wall and a ledge.
 9. The variable vane assembly as set forth in claim 1, for use in a compressor section.
 10. The variable vane assembly as set forth in claim 1, further comprising a means to limit rotation of said vane about a central axis of said trunnion.
 11. The variable vane assembly as set forth in claim 1, wherein said partial flange has a substantially curvic profile in the plane perpendicular to a central axis of said trunnion.
 12. The variable vane assembly as set forth in claim 1, wherein said partial flange has a substantially faceted profile in the plane perpendicular a central axis of said trunnion.
 13. A gas turbine engine comprising: a compressor section; a variable vane assembly in the compressor section, the variable vane assembly including a plurality of vanes each having an inner trunnion and an outer trunnion, wherein said inner trunnion includes a partial flange extending from said inner trunnion for a first limited circumferential extent; an actuator connected to said outer trunnion for causing said vane to pivot to change an angle of incidence; and a shroud comprising a forward axial half and an aft axial half, and supporting said inner trunnions in recesses, wherein said recesses include a retainer portion in the aft axial half receiving said partial flange, and said retainer portion is a recess defined by a bottom wall and a ledge and extending from a central bore for a second limited circumferential extent greater than the first circumferential extent of the partial flange, and wherein said inner trunnion can pivot relative to a central axis of said central bore when said partial flange is received in said retainer portion.
 14. The gas turbine engine as set forth in claim 13, wherein said variable vane assembly further comprises a means to limit rotation of said vane about the central axis.
 15. The gas turbine engine as set forth in claim 13, wherein the variable vane assembly is rotatable to first and second positions, wherein said first and second positions correspond to first and second ends of said second limited circumferential extent, respectively.
 16. The gas turbine engine as set forth in claim 13, wherein said partial flange has a substantially curvic profile in the plane perpendicular to said central axis.
 17. The gas turbine engine as set forth in claim 13, wherein said partial flange has a substantially faceted profile in the plane perpendicular to said central axis.
 18. A variable vane comprising: a vane having an airfoil, the vane having a first end and a second end; a first trunnion attached to said first end of said vane, adapted to accept a force from an actuator to cause a rotational moment to be applied to said vane about a central axis; and a second trunnion attached to said second end of the vane, comprising a first portion that is substantially cylindrical and a partial flange extending from said first portion of said second trunnion for a limited circumferential extent relative to the central axis.
 19. The variable vane as set forth in claim 18, wherein said partial flange has a substantially curvic profile in the plane perpendicular to said central axis.
 20. The variable vane as set forth in claim 18, wherein said partial flange has a substantially faceted profile in the plane perpendicular to said central axis. 